[R-sig-Geo] help with args to CRS(), spTransform

[Roger Bivand]

On Thu, 29 Oct 2009, Michael Denslow wrote:

> Dear List,
>
> I am attending to transform a set of points that are originally in
> latitude longitude (unprojected) to a Lambert Conformal Conic
> projection.
> I am a bit confused about the arguments to CRS and would appreciate any help.

Use one of the EPSG references, www.spatialreference.org, or the built in 
one:

library(rgdal)
EPSG <- make_EPSG()
EPSG[grep("North Carolina", EPSG$note),]

The second one looks promising, so try:

CRS("+init=epsg:3358")

checking on:

http://www.spatialreference.org/ref/epsg/3358/

Hope this helps,

Roger

>
> I have an old file that contains point distances that were measured
> with the following projection information. This is from ArcMap which I
> no longer use. I need to use this old file to compare with my new
> distances.
>
> Projected Coordinate System: NAD_1983_StatePlane_North_Carolina_FIPS_3200
> Projection: Lambert_Conformal_Conic
> False_Easting: 609601.22000000
> False_Northing: 0.00000000
> Central_Meridian: -79.00000000
> Standard_Parallel_1: 34.33333333
> Standard_Parallel_2: 36.16666667
> Latitude_Of_Origin: 33.75000000
> Linear Unit: Meter
>
> Geographic Coordinate System: GCS_North_American_1983
> Datum: D_North_American_1983
> Prime Meridian: Greenwich
> Angular Unit: Degree
>
> I would like the new point distance measurements that I am doing in
> SPATSTAT to be comparable to the old ones that used the projection
> above (in meters?).
>
> Here is what I have attempted...
>
> library(sp)
> library(rgdal)
> # dput(herb.sp) I hope this works I have never used dput() before!
>
> new("SpatialPoints"
>    , coords = structure(c(-81.6809, -78.9455, -77.879, -83.1031, -78.6634,
> -79.057, 36.2147, 35.9982, 34.227, 35.2571, 35.7853, 35.9097), .Dim = c(6L,
> 2L), .Dimnames = list(NULL, c("coords.x1", "coords.x2")))
>    , bbox = structure(c(-83.1031, 34.227, -77.879, 36.2147), .Dim = c(2L,
> 2L), .Dimnames = list(NULL, c("min", "max")))
>    , proj4string = new("CRS"
>    , projargs = " +proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0"
> )
> )
>
> herb.lcc <- spTransform(herb.sp,CRS("+proj=lcc"))
>
>
> I am not sure that this contains all of the arguments needed. I tried
> looking at the PROG.4 manual here:
> ftp://ftp.remotesensing.org/proj/OF90-284.pdf , but I am still unclear
> how to proceed.
>
> Any help would be most appreciated!
> Thanks again,
> Michael
>
>
>
>

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no